Although a lithium-ion secondary battery has advantages such as high working voltage, long service life and fast charging speed and the like, with development of technology and people's demand for fast and convenient electronic products, the lithium-ion secondary battery is required to have better cycle performance, and is also required to be capable of quickly discharging in condition of lower temperature.
In practice, cyclic carbonate ester and chain carbonate ester are usually used as solvent, but the solvent is continuously oxidized or reduced during charging-discharging process of the lithium-ion secondary battery, the first coulombic efficiency of the lithium-ion secondary battery is lower, and the cycle performance of the lithium-ion secondary battery is also deteriorated. U.S. Pat. No. 5,626,981 discloses a method of forming a SEI film on a surface of a negative electrode plate, in which the first coulombic efficiency and the cycle performance of the lithium-ion secondary battery are improved by adding vinylene carbonate (VC) into an electrolyte. However, due to addition of vinylene carbonate (VC), the SEI film formed on the surface of the negative electrode plate will be too thick, the impedance of the SEI film is relative large, therefore the discharging performance in condition of low temperature of the lithium-ion secondary battery would be deteriorated.
Chinese patent application publication No. CN101755354A discloses a method of forming a SEI film on a surface of a negative electrode plate, in which 4-methylene-1,3-dioxolan-2-one is added into an electrolyte, the cycle performance of the lithium-ion secondary battery is improved, but the low temperature discharging performance is not mentioned in this patent document.
Therefore, it is necessary to provide a lithium-ion secondary battery and an electrolyte thereof, which has better cycle performance and better discharging performance in condition of low temperature.